It is well accepted practice to use self-propelled vehicles with articulated booms having a movable platform or basket at the end of the articulated boom and power means for raising, lowering and controllably moving the platform in lateral and horizontal movements. The difficulty is most cases is how to control accurately and without excessive abruptness, the movements of the basket so the operator can easily and conveniently locate the basket precisely and with a degree of speed.
There are, of course, available controls for the power means which accomplish the boom movements but the shortcoming of such controls is that they tend to be lacking in sensitivity and accuracy. Moreover, the controls tend to produce basket movement with a jerkiness when smooth and gradual starting, stopping movements are needed for proper basket placement. This becomes an important consideration since the operator is called upon frequently to make repairs and installation of high voltage lines, for example, and it becomes important to the safety of the basket occupant that the basket be located in a smooth, accurate and efficient manner. These considerations are all essential to take into account and to satisfy, if maximum reliability and utility are to be realized from the self-propelled vertically and horizontally and laterally movable platforms.
It is further important that, should the basket be immobilized for any reason or another because of inability of the operator to function, that the controls at the upper basket level be disabled and that additional controls be available at ground level for lowering the movable platform or basket, such additional controls being independently operatable and fully capable of functioning separate and apart from the controls located in the basket.